On 12 March 2018 at 10:06, Gianmaria Lari <gianmarial...@gmail.com> wrote:
>
>
> On 12 March 2018 at 09:25, David Kastrup <d...@gnu.org> wrote:
>
>> Gianmaria Lari <gianmarial...@gmail.com> writes:
>>
>> > On 11 March 2018 at 10:58, David Kastrup <d...@gnu.org> wrote:
>> >
>> >> Then Scheme expressions written using # in the middle of music are
>> >> expected to be music expressions.
>> >
>> >> If you want to insert an actual
>> >> duration, you need to write it preceded with $ so that it can have
>> >> different type (and trigger different syntactic rules).
>> >>
>> >> But $8 is not a duration. $(ly:make-duration 3 0) would be a duration.
>> >
>> >
>> > How does it work ?
>> > Originary I thought that before source compilation, there was a step
>> where
>> > to replace scheme expressions with their evaluation, like a
>> preprocessor;
>> > that's why I tried c#(+ 6 2). But ok, it's clear it doesn't work in this
>> > way.
>> >
>> > Is this handled by the lilypond parser that create a parse tree and then
>> > according position in the tree and # or $ it expects different types?
>> >
>> > Thank you, g.
>>
>> From the "Extending LilyPond" guide:
>>
>> 1.2.1 LilyPond Scheme syntax
>> ----------------------------
>>
>> The Guile interpreter is part of LilyPond, which means that Scheme can
>> be included in LilyPond input files. There are several methods for
>> including Scheme in LilyPond.
>>
>> The simplest way is to use a hash mark ‘#’ before a Scheme
>> expression.
>>
>> Now LilyPond’s input is structured into tokens and expressions, much
>> like human language is structured into words and sentences. LilyPond
>> has a lexer that recognizes tokens (literal numbers, strings, Scheme
>>
> [....]
>
> Ok David, I think it's clear. Thanks a lot for the very detailed
> explanation, I appreciated your help.
> g.
>
David, in a musical expression the scheme expression #(.....) must return a
musical expression. That's ok.
In case of I'm not inside a musical expression, does lilypond expect that the
scheme expression #(.....) return something compatible with what "is on
the left"?
For example in this (working) code, on the left we have "piece" that needs
a string on the right. So, on the right the scheme expression have to
return a string to have working code. Is my comprehension correct?
\version "2.19.81"
\score { \header { piece = #(number->string 123) } \fixed c' { a a a a} }
Thank you, g.
_______________________________________________
lilypond-user mailing list
lilypond-user@gnu.org
https://lists.gnu.org/mailman/listinfo/lilypond-user
